Apple's Strategy With Color and the iPhone

I don't want to see the low end phones get boring like the high end phones are in terms of color, although it would be nice if the higher end phones had color as well. So here's the question is the reason that the iPhone lower models lower price models have been more colorful is because it works better with that glass. And the reason the ones on the pro models have been less colorful is because they had the frosted glass or is it more just Apple's differentiation between them? I still don't quite understand Apple strategy with color and the iPhone.